How to get Strings after applying two nested string operations

[Raghu9972]

I'm new to data processing and i'm using string operations on a string column to get a string, but i'm getting a dictionary of dictionary.

Ex:

arqueroTable.derive({
    result: `d => op.match(op.match(d['ColA'], '([^s].*a)', 0), 'sample')`,
});

And it is giving the result : [object DictionaryVector], Can somebody help me how can I get it in String?